I. Field of the Invention
The present invention relates to grain carts used in harvesting grain crops. More specifically, the present invention relates to improvements to grain carts to increase the capacity of the grain cart and, at the same time, reduce compaction of the soil of the farm field in which the grain cart is used.
II. Description of the Prior Art
One of the factors that affect the yield of a farm field is the degree to which the soil in the field is compacted. The higher the degree of compaction, the lower the yield. The use of heavy farm equipment in a farm field can cause such compaction resulting in an adverse impact on the yield of the field.
A study was recently performed at Kansas State University relating to the effect of compaction resulting from farm equipment traversing a field. The results of the study suggests that if the farm equipment applies pressure to the soil in excess of 18 pounds per square inch, there is an adverse impact on the field""s yield of up to 10% the next year.
Yield is, of course, only one factor that can be used in evaluating the efficiency of a farm operation. Another significant factor is the time it takes to plant a field, treat the field, and harvest the crop. In the past 50 years, the size and weight of farm equipment has grown significantly. Ideally, such equipment will be designed not only to reduce the time it takes to plant, treat or harvest a field, but also to reduce compaction of the field.
One important piece of equipment used in harvesting grain is the grain cart. Many grain carts made today include a single axle and a pair of wheels. These carts are typically designed to hold 500 to 800 bushels of grain. Other grain carts include a single axle and four wheels mounted to the axle. These carts are designed to hold up to 975 bushels of grain. There are two problems with such grain carts. First, they do not have a large enough capacity. Second, depending upon the load carried by the cart and the wheel size, the pressure applied by the cart to the field can be in the range of 25 pounds per square inch. This pressure exceeds that typical of tractors and various other equipment. The compaction created by such pressure is certainly great enough to adversely effect field yield.
The present invention provides a grain cart with an increased hauling capacity. At the same time, the grain cart of the present invention is designed to reduce the degree of compaction of the field by reducing the pressure applied by the cart to the field. Carts incorporating the present invention can have a capacity of up to 1500 bushels, and thus hold in excess of 50% more grain than prior art carts. At the same time, carts incorporating the present invention provide a maximum pressure to the field in the range of 13 to 15 pounds per square inch. Thus, carts of the present invention provide less compaction force than a typical tractor and less than the 18 pounds per square inch threshold referenced in the Kansas State University study.
The benefits of the present invention discussed above result from the use of either a tandem or tridem axle arrangement. In the tandem axle arrangement, the weight is distributed over two axles and four tires. In the tridem axle arrangement, the weight is distributed over three axles and six tires. In the tandem axle arrangement, the wheels on the back axle pivot so as to be steerable. The wheels on the front axle are not steerable. In the tridem axle arrangement, the wheels on both the front and back axles are steerable and the wheels on the center axle are not steerable. These arrangements allow the cart to have a turning radius approaching that of a single axle cart without the risk of damaging the axles, hubs, wheels and tires while turning. The steerable wheels steer in a controlled fashion. In one embodiment, this steering effect is the result of ground pressure. In another embodiment, a hydraulic power steering system is provided.